A mechanism for ATP-sensitive potassium channel diversity: Functional coassembly of two pore-forming subunits

Cui, Yi; Giblin, Jonathan P.; Clapp, Lucie H.; Tinker, Andrew

doi:10.1073/pnas.98.2.729

Cited by 83 publications

(29 citation statements)

References 36 publications

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“…Identification of Native Hybrid K ATP Channel Activity in Intact Cells-Overexpressed K IR 6.1 and K IR 6.2 co-immunoprecipitate and co-assemble with SUR2B channels (38), which conduct like our hybrid K ATP channels (24). The present results with heteroconcatemeric K IR s demonstrate that all of the possible heteromultimeric K ATP channels are functional and define their basic properties.…”

Section: Nucleotide Regulation Of the K Atp Channel Family 49088mentioning

confidence: 58%

A Conserved Inhibitory and Differential Stimulatory Action of Nucleotides on KIR6.0/SUR Complexes Is Essential for Excitation-Metabolism Coupling by KATP Channels

Babenko

Bryan

2001

Journal of Biological Chemistry

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The mechanism by which ubiquitous adenine nucleotide-gated K IR 6.0 4 /SUR 4 channels link membrane excitability with cellular metabolism is controversial. Is a decreased sensitivity to inhibitory ATP required, or is the Mg-ADP/ATP-dependent stimulatory action of the ATPase, sulfonylurea receptor (SUR), on K IR sufficient to elicit a physiologically significant open channel probability? To evaluate the roles of nucleotide inhibition versus stimulation, we compared K IR 6.1-based K NDP channels with K IR 6.2-based K ATP channels and all possible K IR 6.1/6.2 hybrids. Although K NDP channels are thought to be poorly sensitive to inhibitory ATP and to require Mg-nucleotide diphosphates for activity, we demonstrate that, like K ATP , and hybrid channels, they are inhibited with an IC 50(ATP) 100-fold lower than The primary signaling mechanism that attunes the P O to the cellular metabolic status remains controversial. Observations that K ATP channels burst spontaneously in inside-out patches and show reversible inhibition by submillimolar ATP (4 -6) suggested that opening these K IR s in vivo, in the face of millimolar nucleotide, would necessitate a significant decrease in their sensitivity to ATP. The reduction in the ATP sensitivity of isolated K ATP channels upon treatment with numerous substances has been interpreted as evidence for the plasticity of ATP-inhibitory gating in vivo. Following the report (7) that ATP weakly inhibits K IR 6.2-based channels in the absence of SUR (IC 50(ATP) ϭ ϳ0.2 mM versus ϳ5-20 M with SURs; Refs. 8 and 9), K IR -based plasticity of ATP inhibition has been considered a possible cause of the variable activity observed for K ATP channel isoforms in situ.An alternative idea is that SURs, obligatory regulatory subunits of K ATP channels and members of the ABC superfamily (10, 11), act as nucleotide sensors and, in vivo, SURs would exert a Mg-ADP/ATP-dependent stimulatory action sufficient to overcome the saturated inhibitory effect of nucleotides at noncanonical nucleotide binding site(s) on the K IR (1). This hypothesis is consistent with only a small fraction, ϳ1%, of the maximal NP O for K ATP channel population participating in the regulation of insulin secretion from pancreatic ␤-cells (12) or shortening of action potentials of metabolically inhibited ventricular cardiomyocytes (13,14). The hypothesis is consistent with the marginal effect of a decreased submembrane concentration of ATP on K ATP channel activity in situ, e.g. the enhancement of K ATP currents observed when adenylyl cyclases are maximally stimulated, thus reducing ATP without producing stimulatory MgADP, in cardiomyocytes dialyzed with submillimolar ATP, but not in the perforated patch or conventional whole-cell configuration with millimolar [ATP] i (15). The physiologic significance of the Mg-nucleotide-dependent stimulation of K IR 6.2 has been established by the identification of SUR1 mutations that compromise the stimulatory, but not the inhibitory action of Mg-nucleotides on pancreatic ␤-cell K ATP channels (...

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Section: Nucleotide Regulation Of the K Atp Channel Family 49088mentioning

confidence: 58%

A Conserved Inhibitory and Differential Stimulatory Action of Nucleotides on KIR6.0/SUR Complexes Is Essential for Excitation-Metabolism Coupling by KATP Channels

Babenko

Bryan

2001

Journal of Biological Chemistry

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“…Consistent with previous studies (Kuniyasu et al, 2003;van Bever et al, 2004;Morrissey et al, 2005), our results demonstrated that both Kir6.1 and Kir6.2 were expressed in rat ventricular myocytes. Indeed, it was also reported that a dimer Kir6.1-Kir6.2 construct expressed with SUR2B had channel activity with small-conductance (Cui et al, 2001). However, it still remains to be determined whether the properties of small-conductance K ATP channels in cardiac myocytes pharmacologically resemble the channels formed by Kir6.1/SUR2B coexpression.…”

Section: Discussionmentioning

confidence: 94%

Identification of two types of ATP-sensitive K+ channels in rat ventricular myocytes

Sung

2007

Life Sciences

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“…Following wash steps (4 ϫ 10 min in PBS) coverslips were mounted and analyzed by laser confocal microscopy (Leica Microsystems). The primary antibodies used were mouse anti-GAPDH (1:300), goat anti-PK (1:500), and rabbit anti-Kir6.2 (76A; 1:100; a kind gift from Dr. A. Tinker, The Rayne Institute, University College, London) (15). The secondary antibodies used were Cy2-conjugated donkey anti-mouse IgG, Cy3-conjugated donkey anti-rabbit IgG, Cy3-conjugated donkey anti-goat IgG, or Cy5-conjugated donkey anti-rabbit IgG (Jackson ImmunoResearch).…”

Section: Generation Of Constructs Used For the Two-hybridmentioning

confidence: 99%

The Glycolytic Enzymes, Glyceraldehyde-3-phosphate Dehydrogenase, Triose-phosphate Isomerase, and Pyruvate Kinase Are Components of the KATP Channel Macromolecular Complex and Regulate Its Function

Dhar-Chowdhury

Harrell

Han

et al. 2005

Journal of Biological Chemistry

117

111

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The regulation of ATP-sensitive potassium (K ATP ) channel activity is complex and a multitude of factors determine their open probability. Physiologically and pathophysiologically, the most important of these are intracellular nucleotides, with a long-recognized role for glycolytically derived ATP in regulating channel activity. To identify novel regulatory subunits of the K ATP channel complex, we performed a two-hybrid protein-protein interaction screen, using as bait the mouse Kir6.2 C terminus. Screening a rat heart cDNA library, we identified two potential interacting proteins to be the glycolytic enzymes, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and triose-phosphate isomerase. The veracity of interaction was verified by co-immunoprecipitation techniques in transfected mammalian cells. We additionally demonstrated that pyruvate kinase also interacts with Kir6.2 subunits. The physiological relevance of these interactions is illustrated by the demonstration that native Kir6.2 protein similarly interact with GAPDH and pyruvate kinase in rat heart membrane fractions and that Kir6.2 protein co-localize with these glycolytic enzymes in rat ventricular myocytes. The functional relevance of our findings is demonstrated by the ability of GAPDH or pyruvate kinase substrates to directly block the K ATP channel under patch clamp recording conditions. Taken together, our data provide direct evidence for the concept that key enzymes involved in glycolytic ATP production are part of a multisubunit K ATP channel protein complex. Our data are consistent with the concept that the activity of these enzymes (possibly by ATP formation in the immediate intracellular microenvironment of this macromolecular K ATP channel complex) causes channel closure.K ATP channels act as metabolic sensors of a large diversity of cell types by directly coupling their energy metabolism to cellular excitability. This function serves as a crucial regulatory mechanism in the responses of various cell types to their metabolic demand. For example, K ATP channels mediate insulin release from pancreatic ␤ cells, control the firing rate of glucose-responsive neurons in the ventromedial hypothalamus, and protect neurons during hypoxia. K ATP channels also have unique roles in the cardiovascular system. In the coronary vasculature, they participate in the maintenance of the coronary vascular tone, whereas in cardiac myocytes, K ATP channel modulation causes alterations in action potential duration and induction of arrhythmias during cardiac ischemia (1).The minimum requirement for the formation of a heterologously expressed K ATP channel appears to be the presence of two types of subunits, namely a pore-forming subunit (Kir6.x) belonging to the family of inward rectifying K ϩ channel subunits and a sulfonylurea receptor regulatory subunit, which is a member of the family of ABC-cassette proteins (2). However, ion channels are increasingly realized to be multisubunit macromolecular complexes (3-5). Recent evidence suggest that the K ATP channel pro...

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A mechanism for ATP-sensitive potassium channel diversity: Functional coassembly of two pore-forming subunits

Cited by 83 publications

References 36 publications

A Conserved Inhibitory and Differential Stimulatory Action of Nucleotides on KIR6.0/SUR Complexes Is Essential for Excitation-Metabolism Coupling by KATP Channels

A Conserved Inhibitory and Differential Stimulatory Action of Nucleotides on KIR6.0/SUR Complexes Is Essential for Excitation-Metabolism Coupling by KATP Channels

Identification of two types of ATP-sensitive K+ channels in rat ventricular myocytes

The Glycolytic Enzymes, Glyceraldehyde-3-phosphate Dehydrogenase, Triose-phosphate Isomerase, and Pyruvate Kinase Are Components of the KATP Channel Macromolecular Complex and Regulate Its Function

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